Until recently the standard method of laying generally horizontal pipes and conduits for utilities such as water, gas, electricity and telecommunications was to dig a trench, lay the pipe into it, and backfill. This is labour intensive. It also has the disadvantage that normal use of the ground where the pipes are laid is interrupted for a relatively long period of time. Consequently there has been an increasing use of methods of trenchless pipe-laying, achieved by boring a horizontal hole and drawing the pipe along it.
A number of types of machinery for trenchless pipe laying are currently in use. Generally they take the form of a wheeled trolley which holds a ram or other boring mechanism. A boring head is forced into the ground from above at a shallow angle, and a steering device is used to bring the boring to horizontality when the intended depth has been reached. As boring progresses, work must be interrupted from time to time to attach a new length of drill rod to the string. This is done by hand. Disadvantages that have arisen from existing equipment include:
Difficulties arising from the need to accurately locate the drilling equipment in the desired starting position. The equipment needs to be pulled or pushed by a motor vehicle or manually which increases the setting-up time. In addition if the locating has to be carried out in a busy street it can be dangerous to manoeuvre the equipment without holding up traffic. PA1 Having to manually manipulate lengths of drill rod while drilling into, and removing them when withdrawing from the hole. This is time consuming. Furthermore the necessary manipulation of the drill rods obliges the operator to be in close proximity to the working parts of the drilling mechanism, with attendant risks of accident. PA1 The need for the operator to undertake manual operations involves them in being exposed to the weather conditions as well as physically demanding activities and to the mud resulting from such operations. Such conditions are not conducive to high quality work. They also prevent the operator from paying close attention at all times to what is going on around him. PA1 1. excavating a given length of trench having a longitudinal axis approximating in direction to that the initial direction of the bore; PA1 2. locating a self propelled chassis over the trench; PA1 3. lowering into the trench from the chassis a thrust chamber which occupies most if not all of the given length; PA1 4. causing a ram to urge a drill head forwardly from the thrust chamber along the path of bore by way of a drill connection comprising at least one drill rod serving to demountably couple the drill head to a motive power unit associated with the chassis; PA1 5. enabling the motive power unit to energise the drill head by way of the drill connection to excavate the bore; PA1 6. periodically temporarily stopping the enabling step and damping the drill connection at a point adjacent the trench; PA1 7. disconnecting the ram from last drill rod in the drill connection; PA1 8. transferring by automatic transfer a further drill rod to the drill connection from an indexed supply of such rods located on the chassis; PA1 9. coupling demountably one end of the further drill rod to the drill connection; PA1 10. connecting the ram to the other end to the one end of the further drill rod; PA1 11. unclamping the drill connection; and PA1 12. resuming the enabling step so that the motive power unit powers the drill by way of the drill connection now extended by the further drill rod. PA1 1. a chassis including means for self propulsion; PA1 2. a thrust chamber mounted on the chassis for displacement between an extended position wherein the thrust chamber is located beneath the chassis and a housed position wherein the chassis can move relatively freely; PA1 3. a prime mover to enable a drill connection to transmit driving power from the prime mover to a drilling head demountably coupled to the prime mover by way of a driving connection extending through the thrust chamber; PA1 4. the driving connection comprising a plurality of drill rods demountably coupled end to end; PA1 5. a magazine for a plurality of single drill rods enabling the plurality to be stored on the chassis; PA1 6. a ram for demountable connection to the one end of the drill connection to enable the drill to be displaced by the other end of the drill connection to the one end along a path for a bore extending from the thrust chamber; PA1 7. a clamp to enable the one end of the drill connection, or a part of the connection near the one end, to be damped to enable the ram to disconnected from the one end; and PA1 8. transfer means whereby a drill rod can be withdrawn from the magazine and located at the one end of the drill connection fro demountable connection thereto so as to extend the overall length of the drill connection at least when the ram is disconnected from the one end.
These and other factors have lead to limitations in size and power and machines in current use are generally limited to bores of about 200 mm diameter.